﻿ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixv 



in the slate of Stonesfield, called Bidelphys Bucklandi by Broderip, 

 and Phascolotherium by Owen, manifests so complete an agreement 

 with the living genus Bidelphys in the number of premolar and molar 

 teeth, in the general form of the jaw, and in the extent and po- 

 sition of its inflected angle, that we can hardly doubt its marsupial 

 character, — a conclusion of no small importance, because in this case 

 we have osteological evidence that both the placental and marsupial 

 classes of mammalia were already in being in an early part of the oolitic 

 era, just as opossums now coexist with skunks on the American con- 

 tinent. Several insects, and among them the elytra of beetles, on which 

 these small quadrupeds may have fed, are preserved in the same rock ; 

 and Prof. Owen remarks that some carnivorous quadrupeds of coeval 

 date could scarcely have been wanting to keep down the numbers of 

 the Phascolotheres and Amphitheres, which were probably, like the 

 quadrupeds now most nearly allied to them, quick breeders*. 



By a singular accident, no other bones have been collected of the 

 skeletons of the seven individuals as yet found at Stonesfield, except 

 seven half lower jaws ; a fact, demonstrating in a marked manner the 

 fragmentary nature of the memorials handed down to us of an ancient 

 terrestrial fauna. Yet no small diligence has been used by collectors 

 for more than a quarter of a century to obtain even the smallest iso- 

 lated bones of fish and reptiles from these beds. I can only compare 

 the capricious chance which has hitherto put us in the exclusive 

 possession of these seven jaws, with the equally strange accident re- 

 corded by Dr. Mantell, in his career of discovery in the Wealden. 

 He computed that in the course of twenty years he had found teeth 

 and bones of the Iguanodon which must have belonged to no less than 

 71 distinct individuals, varying in age and magnitude from the rep- 

 tile just burst from the egg, to one of which the femur measured 24 

 inches in circumference. Yet it was not until the relics of all these 

 individuals were known that a solitary example of part of a jaw-bone 

 was obtained. As in other branches of inquiry one invention or 

 discovery usually elicits another of the same kind, so, when at length 

 the first Iguanodon' s jaw had been procured, a second was soon de- 

 tected in a different locality, and then the fragment of a third brought 

 to light from the stores of the British Museum. The solidity of 

 these jaw-bones, and the strength with which several teeth fixed in 



* Brit. Foss. Mamra., Introduction, p. 14. 

 VOL. VII, / 



